ResolvableMiddleware.php

<?php

class ResolvableMiddleware
{
    public function __construct(ContainerInterface $container, $classname)
    {
        $this->container = $container;
        $this->classname = $classname;
    }

    public function handle(RequestInterface $request)
    {
        return $this->container->get($this->classname)->handle($request);
    }
}